Silicon-carbon negative electrode material, negative electrode plate, electrochemical device and electronic device

Abstract

The invention relates to the technical field of electrochemical energy storage devices, in particular to a silicon-carbon negative electrode material, a negative electrode plate, an electrochemical device and an electronic device, and mainly comprises a core material and a coating material, the core material comprises silicon particles, the coating material comprises a porous carbon material doped with indium particles, and the coating material comprises a porous carbon material doped with indium particles. The average pore size of the coating material ranges from 10 nm to 20 nm, and the porosity of the coating material ranges from 35% to 45%. According to the silicon-carbon negative electrode material provided by the invention, the coating material has the effects of buffering and inhibiting silicon volume expansion, so that pulverization of the silicon-carbon negative electrode material is inhibited, and the problem of volume expansion of a battery is solved.

Description

Technical Field

[0001] This application relates to the field of electrochemical energy storage device technology, and particularly to silicon-carbon anode materials, anode sheets, electrochemical devices, and electronic devices. Background Technology

[0002] Silicon-based anode materials are considered a key breakthrough for next-generation batteries due to their theoretical specific capacity of up to 4200 mAh / g. However, during battery charging and discharging, silicon-based anode materials are prone to volume expansion due to lithium insertion / extraction, leading to problems such as anode material pulverization, electrode structure collapse, and continuous rupture and regeneration of the SEI film, which affect the battery's rate capability, cycle life, and initial coulombic efficiency.

[0003] Therefore, it is urgent to improve the volume expansion problem of silicon-based anode materials. Summary of the Invention

[0004] Based on the shortcomings of existing technologies, this application provides silicon-carbon anode materials, anode sheets, electrochemical devices, and electronic devices, aiming to improve the volume expansion problem of silicon-based anode materials.

[0005] To achieve the above objectives, this application provides a silicon-carbon anode material, which includes a core material and a coating material. The core material includes silicon particles, and the coating material includes a porous carbon material doped with indium particles. The average pore size of the coating material is 10 nm to 20 nm, and the porosity of the coating material is 35% to 45%.

[0006] In some embodiments, the specific surface area of ​​the coating material is 90 m². 2 / g to 140m 2 / g.

[0007] In some embodiments, the average volumetric particle size of the indium particles is 1 nm to 5 nm.

[0008] In some embodiments, the mass ratio of the indium particles is a, based on the mass of the porous carbon material, where 6.67% ≤ a ≤ 10%.

[0009] In some embodiments, the volumetric particle size Dv50 of the silicon particles is 10 nm to 15 nm.

[0010] In some embodiments, the particle size distribution (Dv90-Dv10) / Dv50 of the silicon particles is ≤1.2.

[0011] In some embodiments, the mass ratio of the silicon particles is b, based on the mass of the silicon-carbon anode material, where 35% ≤ b ≤ 45%.

[0012] This application also provides a negative electrode sheet, which includes the silicon-carbon negative electrode material.

[0013] In some embodiments, the negative electrode sheet further includes a conductive agent and a binder, wherein the mass ratio of the silicon-carbon negative electrode material, the conductive agent and the binder is (5-9):(1-5):(1-3).

[0014] This application also provides an electrochemical device, which includes the negative electrode plate.

[0015] This application also provides an electronic device, which includes any of the electrochemical devices described herein.

[0016] The beneficial effects of this application are as follows:

[0017] This application controls the average pore size and porosity of the coating material of the silicon-carbon anode material, enabling its mesopores to accommodate the volume expansion of silicon particles during lithium intercalation. This, in conjunction with the In-C bonding interface between the porous carbon material and indium particles, buffers and suppresses the volume expansion of silicon particles, thereby inhibiting the pulverization of the silicon-carbon anode material and reducing the expansion rate of the battery. At the same time, its mesopores can also improve ion transport channels, and the indium enriched on the surface of the mesopores acts as an ion sieve layer, which can adsorb lithium salt anions, facilitating lithium ion transport and thus improving the rate performance of the battery. Detailed Implementation

[0018] The term "polymer" refers to a polymeric compound prepared by polymerizing the same or different types of monomers. The general term "polymer" includes the terms "homopolymer," "copolymer," "trimer," and "interpolymer."

[0019] The term "binder" refers to a substance used for interfacial interactions to firmly bond two or more materials together. This document may use any organic binder that can bond polymers to porous substrate materials or to each other.

[0020] The term "particle size distribution SPAN value" refers to the (Dv90-Dv10) / Dv50 value of a material particle, a dimensionless parameter used to measure the width or dispersion of particle size distribution. Here, Dv10, Dv50, and Dv90 represent the particle size values ​​corresponding to 10%, 50%, and 90% of the cumulative volume of the material particles, respectively.

[0021] The term "specific surface area" refers to the total surface area of ​​a unit mass of a substance.

[0022] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application. The embodiments of this application may omit unnecessary detailed descriptions. For example, detailed descriptions of well-known matters and repeated descriptions of actually identical structures may be omitted. This is to avoid making the following description unnecessarily lengthy and to facilitate understanding by those skilled in the art.

[0023] In this application, the technical features described in an open-ended manner include both closed-ended technical solutions composed of the listed features and open-ended technical solutions composed of the listed features. In this application, numerical ranges are involved; unless otherwise specified, the numerical ranges are considered continuous and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, just as any upper limit can be combined with any other upper limit to form an unspecified range. Furthermore, each individually disclosed point or single value can itself serve as a lower or upper limit and be combined with any other point or single value or with other lower or upper limits to form an unspecified range.

[0024] It should be noted that, in the specific embodiments of this application, lithium-ion batteries are used as an example of electrochemical devices to explain this application, but the electrochemical devices of this application are not limited to lithium-ion batteries.

[0025] Silicon-based anode materials are considered a key breakthrough for next-generation batteries due to their theoretical specific capacity of up to 4200 mAh / g. However, during battery charging and discharging, silicon-based anode materials are prone to volume expansion due to lithium insertion / extraction, leading to problems such as anode material pulverization, electrode structure collapse, and continuous rupture and regeneration of the SEI film, which affect the battery's rate capability, cycle life, and initial coulombic efficiency.

[0026] Therefore, it is urgent to improve the volume expansion problem of silicon-based anode materials.

[0027] Based on the shortcomings of existing technologies, this solution provides silicon-carbon anode materials, anode sheets, electrochemical devices, and electronic devices, aiming to improve the volume expansion problem of silicon-based anode materials.

[0028] To achieve the above objectives, this solution provides a silicon-carbon anode material, which includes a core material and a coating material. The core material includes silicon particles, and the coating material includes a porous carbon material doped with indium particles. The average pore size of the coating material is 10 nm to 20 nm, and the porosity of the coating material is 35% to 45%.

[0029] This solution utilizes porous carbon materials to form an In-C bonding interface with indium particles, serving as an interface buffer layer to replace physical coating. This buffers and suppresses the volume expansion of silicon particles, thereby inhibiting the pulverization of silicon-carbon anode materials and improving battery volume expansion. Simultaneously, indium particles not only construct a bridging conductive network to improve the conductivity of the anode, thus improving the battery's rate and cycle performance, but also accumulate on the surface of the mesopores in the coating material of the silicon-carbon anode material, acting as an ion sieve layer to adsorb lithium salt anions in the electrolyte, promoting rapid lithium ion transport and further improving the battery's rate performance.

[0030] In silicon-carbon anode materials, controlling the lower limit of the average pore size of the coating material to 10 nm not only allows the mesopores to accommodate the volume-expanding silicon particles during lithium intercalation, mitigating the volume expansion of silicon particles and thus reducing the battery's expansion rate, but also improves ion transport channels, facilitating lithium-ion transport and thereby enhancing the battery's rate performance. Further controlling the upper limit of the average pore size of the coating material to 20 nm not only prevents silicon particles from escaping from the mesopores and affecting the suppression of silicon particle volume expansion, thus reducing the battery's expansion rate, but also reduces the contact area between the electrolyte and silicon particles, which helps reduce the occurrence of side reactions, thereby inhibiting excessive growth of the SEI film and ultimately improving the battery's cycle life.

[0031] For example, the average pore size of the coating material is 10.0 nm, 10.5 nm, 11.0 nm, 11.5 nm, 12.0 nm, 12.5 nm, 13.0 nm, 13.5 nm, 14.0 nm, 14.5 nm, 15.0 nm, 15.5 nm, 16.0 nm, 16.5 nm, 17.0 nm, 17.5 nm, 18.0 nm, 18.5 nm, 19.0 nm, 19.5 nm, 20.0 nm, or falls within the range of any two of the above values.

[0032] In silicon-carbon anode materials, setting the lower limit of the porosity of the coating material at 35% not only increases the space for silicon particle volume expansion and ion transport channels, thus improving battery volume expansion and rate performance, but also helps maintain the stability of the pore structure of the coating material. This prevents stress concentration-induced pore cracks that could lead to anode structure collapse and affect battery cycle stability. Furthermore, setting the upper limit of the porosity at 45% helps control the contact area between the electrolyte and silicon, reducing side reactions and inhibiting excessive SEI film growth, thereby improving battery cycle life.

[0033] For example, the porosity of the coating material is 35.0%, 35.5%, 36.0%, 36.5%, 37.0%, 37.5%, 38.0%, 38.5%, 39.0%, 39.5%, 40.0%, 40.5%, 41.0%, 41.5%, 42.0%, 42.5%, 43.0%, 43.5%, 44.0%, 44.5%, 45.0%, or within the range of any two of the above values.

[0034] In silicon-carbon anode materials, by controlling the average pore size and porosity of the coating material, the mesopores can accommodate the volume-expanding silicon particles during lithium intercalation. Combined with the In-C bonding interface between the porous carbon material and indium particles, the volume expansion of silicon particles is buffered and suppressed, thereby inhibiting the pulverization of silicon-carbon anode materials and improving the volume expansion of the battery. At the same time, the indium enriched on the surface of the mesopores acts as an ion sieve layer, adsorbing lithium salt anions in the electrolyte, promoting the rapid transport of lithium ions in the mesopores, effectively improving ion transport efficiency, thereby improving the rate performance of the battery. Furthermore, indium particles can construct a bridging conductive network, improving the conductivity of silicon-carbon anode materials, further improving the rate and cycle performance of the battery.

[0035] In some embodiments, the specific surface area of ​​the coating material is 90 m². 2 / g to 140m 2 / g.

[0036] In silicon-carbon anode materials, the lower limit of the specific surface area of ​​the coating material is controlled at 90 μm². 2 / g helps improve lithium-ion channels and increase ion diffusion rate, thereby improving the rate performance of the battery. Furthermore, the upper limit of the specific surface area of ​​the coating material is controlled at 140m². 2 / g not only helps to regulate the pore distribution of the coating material and maintain the overall structural stability of the silicon-carbon anode material, but also helps to suppress the volume expansion of silicon particles, thereby improving the volume expansion of the battery. It can also reduce the contact area between the electrolyte and silicon particles, inhibit the growth of the SEI film, and thus improve the cycle capacity retention rate of the battery.

[0037] For example, the specific surface area of ​​the coating material is 90 m². 2 / g、92m 2 / g、94m 2 / g、96m 2 / g、98m 2 / g, 100m 2 / g、102m 2 / g, 104m 2 / g, 106m 2 / g, 108m 2 / g、110m 2 / g、112m 2 / g、114m 2 / g、116m 2 / g、118m 2 / g, 120m 2 / g、122m 2 / g、124m 2 / g、126m 2 / g、128m 2 / g、130m 2 / g、132m 2 / g、134m 2 / g、136m 2 / g、138m 2 / g, 140m 2 / g, or within the range of any two of the above values.

[0038] In some embodiments, the average volumetric particle size of the indium particles is 1 nm to 5 nm.

[0039] The lower limit of the average volumetric particle size of indium is set to 1 nm, which helps indium to be evenly dispersed in silicon-carbon anode materials. This promotes the formation of In-C bonds between porous carbon materials and indium. Combined with the porous structure, it buffers and suppresses the volume expansion of silicon particles and acts as an ion sieve to adsorb lithium salt anions, improving lithium-ion transport efficiency and thus improving the rate performance of the battery. At the same time, the upper limit of the average volumetric particle size of indium is set to 5 nm. This controls the indium content and suppresses indium agglomeration. While suppressing the volume expansion of silicon particles, it also reduces the risk of pore blockage in the coating material, thereby improving the ion transport channels.

[0040] For example, the average volumetric particle size of the indium particles is 1.00 nm, 1.20 nm, 1.40 nm, 1.60 nm, 1.80 nm, 2.00 nm, 2.20 nm, 2.40 nm, 2.60 nm, 2.80 nm, 3.00 nm, 3.20 nm, 3.40 nm, 3.60 nm, 3.80 nm, 4.00 nm, 4.20 nm, 4.40 nm, 4.60 nm, 4.80 nm, 4.90 nm, 4.92 nm, 4.94 nm, 4.96 nm, 4.98 nm, or 5.00 nm, or falls within the range of any two of the above values.

[0041] In some implementations, the mass ratio of indium particles is a, based on the mass of the porous carbon material, where 6.67% ≤ a ≤ 10%.

[0042] In silicon-carbon anode materials, based on the mass of porous carbon material, the lower limit of the indium particle mass ratio is controlled at 6.67%. This promotes the formation of In-C bonds between the porous carbon material and indium. Building upon the porous structure of the coating material, indium's superplasticity actively absorbs volume stress, buffering and suppressing the volume expansion of silicon particles, thereby inhibiting the pulverization of the silicon-carbon anode material and improving the battery's volume expansion problem. Simultaneously, indium is used to construct a bridging conductive network, improving the conductivity of the anode, thus improving the battery's rate and cycle performance. Furthermore, the indium enriched on the mesopore surface of the coating material acts as an ion sieve, adsorbing lithium salt anions in the electrolyte and promoting rapid lithium ion transport within the mesopores of the coating material, thereby improving the battery's rate performance. Further controlling the indium particle mass ratio to an upper limit of 10% reduces the risk of pore blockage caused by indium agglomeration, further improving ion transport and thus enhancing the battery's rate performance.

[0043] For example, 'a' is 6.67%, 6.68%, 6.69%, 6.70%, 6.75%, 6.80%, 6.85%, 6.90%, 6.95%, 7.00%, 7.10%, 7.20%, 7.30%, 7.40%, 7.50%, 7.60%, 7.70%, 7.80%, 7.90%, 8.00%, 8.10%, 8 0.20%, 8.30%, 8.40%, 8.50%, 8.60%, 8.70%, 8.80%, 8.90%, 9.00%, 9.10%, 9.20%, 9.30%, 9.40%, 9.50%, 9.60%, 9.70%, 9.80%, 9.90%, 10.00%, or within the range of any two of the above values.

[0044] In some implementations, the volumetric particle size Dv50 of the silicon particles is 10 nm to 15 nm.

[0045] In silicon-carbon anode materials, the lower limit of the volumetric particle size Dv50 of silicon particles is 10 nm. The average pore size and porosity of the coating material allow the mesopores of the coating material to accommodate the volume-expanded silicon particles during lithium intercalation, thereby reducing the battery expansion rate. Furthermore, the upper limit of the volumetric particle size Dv50 of silicon particles is controlled to 15 nm, which promotes the dispersion of silicon particles in the silicon-carbon anode material, facilitates electron and ion transport, and improves the rate performance of the battery. Moreover, the volume of silicon particle expansion can be controlled, which helps to improve the volume expansion of silicon particles in silicon-carbon anode materials, thereby improving the volume expansion of the battery.

[0046] For example, the volumetric particle size Dv50 of the silicon particles is 10.0 nm, 10.2 nm, 10.4 nm, 10.6 nm, 10.8 nm, 11.0 nm, 11.2 nm, 11.4 nm, 11.6 nm, 11.8 nm, 12.0 nm, 12.2 nm, 12.4 nm, 12.6 nm, 12.8 nm, 13.0 nm, 13.2 nm, 13.4 nm, 13.6 nm, 13.8 nm, 14.0 nm, 14.2 nm, 14.4 nm, 14.6 nm, 14.8 nm, 15.0 nm, or falls within the range of any two of the above values.

[0047] In some implementations, the particle size distribution SPAN value (Dv90-Dv10) / Dv50 of the silicon particles is ≤1.2.

[0048] The upper limit of the SPAN value of silicon particle size distribution is 1.2 to avoid uneven volume expansion of the battery due to uneven silicon particle size distribution, thereby helping to maintain the cycle life of the battery. In addition, reducing the SPAN value of silicon particle size distribution can improve the uniformity of silicon particle size, which not only uniformly improves the energy density of the battery and promotes electron and ion transport, thereby improving the rate performance of the battery, but also helps the coating material to improve the volume expansion of silicon.

[0049] For example, the SPAN values ​​for the silicon particle size distribution are 0, 0.02, 0.04, 0.06, 0.08, 0.10, 0.12, 0.14, 0.16, 0.18, 0.20, 0.22, 0.24, 0.26, 0.28, 0.30, 0.32, 0.34, 0.36, 0.38, 0.40, 0.42, 0.44, 0.46, 0.48, 0.50, 0.52, 0.54, 0.56, 0.58, and 0.60. The values ​​are 0.62, 0.64, 0.66, 0.68, 0.70, 0.72, 0.74, 0.76, 0.78, 0.80, 0.82, 0.84, 0.86, 0.88, 0.90, 0.92, 0.94, 0.96, 0.98, 1.00, 1.02, 1.04, 1.06, 1.08, 1.10, 1.12, 1.14, 1.16, 1.18, 1.20, or within the range of any two of the above values.

[0050] In some implementations, based on the mass of the silicon-carbon anode material, the mass ratio of silicon particles is b, where 35% ≤ b ≤ 45%.

[0051] Based on the quality of the silicon-carbon anode material, the mass ratio of silicon particles is b. The lower limit of b is controlled at 35%. By increasing the amount of silicon added, the energy density of the battery can be improved by utilizing the high theoretical specific capacity of silicon, thereby improving the initial coulombic efficiency of the battery. The upper limit of b is controlled at 45% to control the volume expansion of silicon particles. Thus, under the action of the coating material, the volume expansion of silicon particles is suppressed and buffered, thereby suppressing the pulverization of silicon-carbon anode material and improving the volume expansion of the battery.

[0052] For example, b is 35.0%, 35.2%, 35.4%, 35.6%, 35.8%, 36.0%, 36.2%, 36.4%, 36.6%, 36.8%, 37.0%, 37.2%, 37.4%, 37.6%, 37.8%, 38.0%, 38.2%, 38.4%, 38.6%, 38.8%, 39.0%, 39.2%, 39.4%, 39.6%, 39.8%, 40.0%, and 40%. 2%, 40.4%, 40.6%, 40.8%, 41.0%, 41.2%, 41.4%, 41.6%, 41.8%, 42.0%, 42.2%, 42.4%, 42.6%, 42.8%, 43.0%, 43.2%, 43.4%, 43.6%, 43.8%, 44.0%, 44.2%, 44.4%, 44.6%, 44.8%, 45.0%, or within the range of any two of the above values.

[0053] In some embodiments, the preparation method of silicon-carbon anode material includes the following steps:

[0054] Silicon particles are obtained by modifying the silicon source with a surface modifier;

[0055] The carbon source, indium compound, silicon particles and pore-forming agent are mixed and dried, and then treated at high temperature to obtain silicon-carbon anode material.

[0056] This method modifies the silicon source with a surface modifier, which helps to disperse the silicon source. As a result, the silicon particles are uniformly dispersed in the silicon-carbon anode material after preparation, which is beneficial to the silicon-carbon anode material for improving the volume expansion of silicon particles. Subsequently, through mixing and high-temperature treatment, the carbon source is pyrolyzed and carbonized to form a porous carbon material that coats the surface of the silicon particles. Furthermore, the volatilization of the pore-forming agent creates pores on the porous carbon material, and the indium compound is reduced and incorporated into the porous carbon material to form a silicon-carbon anode material with a porous structure.

[0057] In some embodiments, the silicon source includes at least one of micron-sized silicon powder, nano-sized silicon powder, and silicon suboxide.

[0058] This solution does not impose any particular restrictions on the silicon source, which can be any silicon source known in the prior art, as long as it can achieve the purpose of this application. For example, it can include, but is not limited to, at least one of the silicon sources mentioned above.

[0059] In some embodiments, the surface modifier includes cationic surfactants and / or silane coupling agents.

[0060] In some embodiments, the surface modifier includes at least one of hexaalkyltrimethylammonium bromide, sodium lignosulfonate, sodium methylene diphenylsulfonate, sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, sodium dodecyl sulfonate, polyol esters, fatty acid glycerides, oleic acid, oleylamine, oleamide, stearic acid, polysorbate, polyethylene glycol octylphenyl ether, alkylsilane coupling agents, aminosilane coupling agents, alkenylsilane coupling agents, epoxyalkylsilane coupling agents, and alkylacryloyloxysilane coupling agents.

[0061] Cationic surfactants adsorb onto the surface of the silicon source through electrostatic interactions, imparting a positive charge to the silicon source. This facilitates the uniform mixing of the silicon source with other components, thereby improving the dispersibility of silicon particles in the silicon-carbon anode material. Meanwhile, silane coupling agents chemically connect hydroxyl groups on the surface of the silicon source to organic groups, altering the surface properties of the silicon source and improving its compatibility with the organic matrix. This further enhances the dispersion of silicon particles in the silicon-carbon anode material.

[0062] This solution does not impose any particular restrictions on the surface modifier, which can be any surface modifier known in the prior art, as long as it can achieve the purpose of this application. For example, it can include, but is not limited to, at least one of the surface modifiers mentioned above.

[0063] In some implementations, the mass ratio of silicon source to surface modifier is (2-5):1.

[0064] The mass ratio of silicon source to surface modifier is 2:1. Adjusting the amount of surface modifier added reduces the introduction of excess components during the preparation of silicon-carbon anode materials, thereby improving the quality of silicon-carbon anode materials. On the other hand, the mass ratio of silicon source to surface modifier is 5:1. Increasing the amount of surface modifier added improves the modification effect on silicon source, which is beneficial to improving the dispersibility of silicon particles.

[0065] For example, the mass ratio of silicon source to surface modifier is 2:1, 3:1, 4:1, 5:1, or within any two of the above values.

[0066] In some embodiments, the modification includes: dispersing a silicon source with a surface modifier, followed by filtration and drying.

[0067] In some embodiments, dispersion includes stirring and / or sonication, and the dispersion time is 20 min to 40 min; and / or,

[0068] The drying temperature is 50°C to 70°C; and / or the drying time is 10h to 15h.

[0069] For example, the dispersion time is 20 min, 22 min, 24 min, 26 min, 28 min, 30 min, 32 min, 34 min, 36 min, 38 min, 40 min, or within any two of the above values.

[0070] For example, the drying temperature is 50°C, 52°C, 54°C, 56°C, 58°C, 60°C, 62°C, 64°C, 66°C, 68°C, 70°C, or within any two of the above values.

[0071] For example, the drying time is 10.0h, 10.5h, 11.0h, 11.5h, 12.0h, 12.5h, 13.0h, 13.5h, 14.0h, 14.5h, 15h, or within any two of the above values.

[0072] By controlling the surface modifier and modification parameters, the surface properties of the silicon source can be changed, and the compatibility between the silicon source and carbon sources can be improved, thereby facilitating the dispersion of silicon particles in silicon-carbon anode materials.

[0073] This solution does not impose any particular restrictions on the modification method of the silicon source. It can be any modification method of the silicon source known in the prior art, as long as it can achieve the purpose of this application. For example, it can include, but is not limited to, at least one of the above-mentioned silicon source modification methods.

[0074] In some embodiments, the carbon source includes at least one of polyvinylpyrrolidone, polyvinyl alcohol, starch, and polyethyleneimine.

[0075] This method promotes the pyrolysis and carbonization of carbon source to form porous carbon material, which is then coated on the surface of silicon particles through mixing and high-temperature treatment. Combined with pore-forming agents, indium compounds, and process parameter control, a silicon-carbon anode material with a porous structure is obtained.

[0076] This solution does not impose any particular restrictions on the carbon source, which can be any carbon source known in the prior art, as long as it can achieve the purpose of this application. For example, it can include, but is not limited to, at least one of the carbon sources mentioned above.

[0077] In some embodiments, the indium compound includes at least one of In2O3, In(OH)3, and InCl3.

[0078] This scheme achieves uniform distribution of indium compounds in a carbon source through mixing, and by controlling the pore-forming agent, carbon source, and process parameters, it promotes the reduction of indium compounds to form fine indium nanoclusters, which are then doped into porous carbon materials. This forms an indium-doped carbon coating on the surface of silicon particles, achieving an In-C bonding interface and replacing physical coating, thereby alleviating and suppressing the volume expansion of silicon.

[0079] This solution does not impose any particular restrictions on the indium compound; it can be any indium compound known in the prior art, as long as it can achieve the purpose of this application. For example, it can include, but is not limited to, at least one of the indium compounds mentioned above.

[0080] In some implementations, the mass of the indium compound is c, which is 0.008 to 0.016, based on the mass of the carbon source.

[0081] Based on the mass of the carbon source, the mass of the indium compound is c, with a lower limit of c of 0.008. This is beneficial for increasing the indium content in the silicon-carbon anode material, enabling indium to suppress silicon volume expansion and to act as a conductor and ion sieve, thereby improving the battery's volume expansion, rate performance, and cycle performance. Furthermore, controlling the upper limit of c to 0.016 maintains the improving effect of indium while reducing the risk of indium agglomeration clogging the pores of the silicon-carbon anode material, improving ion channels, and thus enhancing the battery's rate performance.

[0082] For example, c is 0.008, 0.009, 0.010, 0.011, 0.012, 0.013, 0.014, 0.015, 0.016, or falls within the range of any two of the above values.

[0083] In some embodiments, the pore-forming agent includes at least one selected from elemental sulfur, cyclodextrin, cyclohexanol, polyvinylpyrrolidone, glycerol, phosphoric acid, zinc chloride, potassium hydroxide, and potassium carbonate.

[0084] This method utilizes the property of pore-forming agents to sublimate or volatilize at high temperatures to create pores in porous carbon materials, thus forming silicon-carbon anode materials with porous structures.

[0085] This solution does not impose any particular restrictions on the pore-forming agent; it can be any pore-forming agent known in the prior art, as long as it can achieve the purpose of this application. For example, it can include, but is not limited to, at least one of the pore-forming agents mentioned above.

[0086] In some embodiments, the mass ratio of the pore-forming agent is d, which is 10% to 20%, based on the total mass of the carbon source, indium compound, silicon particles, and pore-forming agent.

[0087] Based on the total mass of carbon source, indium compound, silicon particles and pore-forming agent, the mass ratio of pore-forming agent is d. The lower limit of d is adjusted to 10%, which helps to increase the porosity and pore size of the coating material. This enables the mesopores of the coating material to directionally accommodate the volume expansion of silicon particles during lithium intercalation, thus improving the volume expansion of the battery. At the same time, the upper limit of d is adjusted to 20%, which controls the porosity of the coating material and helps to maintain the structural stability of its pores, avoiding the collapse of the negative electrode structure during battery cycling and affecting the cycle life of the battery.

[0088] For example, d is 10.0%, 10.5%, 11.0%, 11.5%, 12.0%, 12.5%, 13.0%, 13.5%, 14.0%, 14.5%, 15.0%, 15.5%, 16.0%, 16.5%, 17.0%, 17.5%, 18.0%, 18.5%, 19.0%, 19.5%, 20.0%, or falls within the range of any two of the above values.

[0089] In some embodiments, the mixing temperature is 45°C to 65°C; and / or the mixing time is 10h to 15h.

[0090] For example, the mixing temperature is 45℃, 46℃, 47℃, 48℃, 49℃, 50℃, 51℃, 52℃, 53℃, 54℃, 55℃, 56℃, 57℃, 58℃, 59℃, 60℃, 61℃, 62℃, 63℃, 64℃, 65℃, or within any two of the above values.

[0091] For example, the mixing time is 10.0h, 10.5h, 11.0h, 11.5h, 12.0h, 12.5h, 13.0h, 13.5h, 14.0h, 14.5h, 15.0h, or within any two of the above values.

[0092] This solution does not impose any particular limitation on the mixing steps, which can be any mixing steps known in the prior art, as long as they can achieve the purpose of this application. For example, it can include, but is not limited to, at least one of the above-mentioned mixing steps.

[0093] In some embodiments, the drying temperature is 70°C to 90°C; and / or the drying time is 10h to 15h.

[0094] For example, the drying temperature is 70℃, 71℃, 72℃, 73℃, 74℃, 75℃, 76℃, 77℃, 78℃, 79℃, 80℃, 81℃, 82℃, 83℃, 84℃, 85℃, 86℃, 87℃, 88℃, 89℃, or 90℃, or falls within the range of any two of the above values.

[0095] For example, the drying time is 10.0h, 10.5h, 11.0h, 11.5h, 12.0h, 12.5h, 13.0h, 13.5h, 14.0h, 14.5h, 15.0h, or within any two of the above values.

[0096] This solution does not impose any particular restrictions on the drying steps, which can be any drying steps known in the prior art, as long as they can achieve the purpose of this application. For example, it can include, but is not limited to, at least one of the drying steps described above.

[0097] This method promotes the uniform dispersion of carbon source, indium compound, silicon particles and pore-forming agent through mixing, drying and parameter control, so as to achieve precise positioning of indium and porous structure in the coating material.

[0098] In some embodiments, the high-temperature treatment temperature is 630°C to 670°C; and / or,

[0099] The heating rate for high-temperature treatment is 3°C / min to 8°C / min; and / or,

[0100] The high-temperature treatment time is 1.5 hours to 3 hours; and / or,

[0101] High-temperature treatment is carried out under an inert gas atmosphere; and / or,

[0102] Inert gases include at least one of nitrogen, helium, argon, and neon.

[0103] For example, the high-temperature treatment temperature is 630℃, 632℃, 634℃, 636℃, 638℃, 640℃, 642℃, 644℃, 646℃, 648℃, 650℃, 652℃, 654℃, 656℃, 658℃, 660℃, 662℃, 646℃, 666℃, 668℃, 670℃, or within the range of any two of the above values.

[0104] For example, the heating rate of the high-temperature treatment is 3.0℃ / min, 3.2℃ / min, 3.4℃ / min, 3.6℃ / min, 3.8℃ / min, 4.0℃ / min, 4.2℃ / min, 4.4℃ / min, 4.6℃ / min, 4.8℃ / min, 5.0℃ / min, 5.2℃ / min, 5.4℃ / min, 5.6℃ / min, 5.8℃ / min, 6.0℃ / min, 6.2℃ / min, 6.4℃ / min, 6.6℃ / min, 6.8℃ / min, 7.0℃ / min, 7.2℃ / min, 7.4℃ / min, 7.6℃ / min, 7.8℃ / min, 8.0℃ / min, or within any two of the above values.

[0105] For example, the high-temperature treatment time is 1.5h, 1.6h, 1.7h, 1.8h, 1.9h, 2.0h, 2.1h, 2.2h, 2.3h, 2.4h, 2.5h, 2.6h, 2.7h, 2.8h, 2.9h, or 3.0h, or falls within the range of any two of the above values.

[0106] This scheme uses high-temperature treatment and parameter control to induce the carbon source to pyrolyze and carbonize into porous carbon material, which is then coated on the surface of silicon particles. Furthermore, the volatilization of the pore-forming agent creates pores on the porous carbon material, and the indium compound is reduced at high temperature and incorporated into the porous carbon material, thus forming a silicon-carbon anode material with a porous structure coating.

[0107] In some embodiments, the pore-forming agent is elemental sulfur, and the high-temperature treatment temperature is 650°C. This scheme utilizes the property that elemental sulfur sublimates at 650°C, and the property that indium compounds are reduced in situ to indium particles at 650°C and that indium has a melting point of 156°C, to simultaneously achieve sulfur pore formation and indium doping at 650°C, avoiding high-temperature phase separation, forming extremely small indium nanoclusters that are uniformly embedded in the porous carbon material.

[0108] This solution does not have any particular limitation on high-temperature treatment, which can be any drying step known in the prior art, as long as it can achieve the purpose of this application. For example, it can include, but is not limited to, at least one of the high-temperature treatments described above.

[0109] In some embodiments, the preparation method includes ball milling after high-temperature treatment;

[0110] The ball-to-material mass ratio for ball milling is 1:(30–40); and / or,

[0111] The ball milling speed is 300 r / min to 400 r / min; and / or,

[0112] The ball milling process takes 4 to 8 hours.

[0113] For example, the ball-to-material mass ratio in the ball milling process is 1:30, 1:31, 1:32, 1:33, 1:34, 1:35, 1:36, 1:37, 1:38, 1:39, 1:40, or falls within any two of the above values.

[0114] For example, the ball milling speed is 300 r / min, 305 r / min, 310 r / min, 315 r / min, 320 r / min, 325 r / min, 330 r / min, 335 r / min, 340 r / min, 345 r / min, 350 r / min, 355 r / min, 360 r / min, 365 r / min, 370 r / min, 375 r / min, 380 r / min, 385 r / min, 390 r / min, 395 r / min, 400 r / min, or within any two of the above values.

[0115] For example, the ball milling time is 4.0h, 4.2h, 4.4h, 4.6h, 4.8h, 5.0h, 5.2h, 5.4h, 5.6h, 5.8h, 6.0h, 6.2h, 6.4h, 6.6h, 6.8h, 7.0h, 7.2h, 7.4h, 7.6h, 7.8h, 8.0h, or within any two of the above values.

[0116] After high-temperature treatment, ball milling and parameter adjustment are used to crush any large agglomerates that may form, reduce the particle size of the coating material, increase its specific surface area, thereby improving the ion diffusion rate of the silicon-carbon anode material and improving the rate performance of the battery.

[0117] This solution does not impose any particular restrictions on the preparation method of silicon-carbon anode material. It can be any preparation method of silicon-carbon anode material known in the prior art, as long as it can achieve the purpose of this application. For example, it can include, but is not limited to, at least one of the above-mentioned preparation methods of silicon-carbon anode material.

[0118] This solution also provides a negative electrode sheet, which includes any of the silicon-carbon negative electrode materials described herein.

[0119] In some embodiments, the negative electrode sheet further includes a conductive agent and a binder, and the mass ratio of silicon-carbon negative electrode material, conductive agent and binder is (5-9):(1-5):(1-3).

[0120] By comprehensively regulating the mass ratio of silicon-carbon anode material, conductive agent, and binder within the above range, the energy density of the battery can be improved through silicon-carbon anode material. At the same time, controlling the content of conductive agent and binder not only improves the conductivity of the anode, thereby reducing the internal resistance of the battery and helping to improve the rate performance of the battery, but also improves the adhesion between the anode active material layer and the current collector, inhibits the pulverization of the anode active material layer, and thus improves the battery cycle performance.

[0121] For example, the mass ratio of silicon-carbon anode material, conductive agent, and binder is 5:1:1, 6:1:1, 7:1:1, 8:1:1, 9:1:1, 5:2:1, 6:2:1, 7:2:1, 8:2:1, 9:2:1, 5:3:1, 6:3:1, 7:3:1, 8:3:1, 9:3:1, 5:4:1, 6:4:1, 7:4:1, 8:4:1, 9:4:1, 5:5:1, 6:5:1, 7:5:1, 8:5:1, 9:5:1, 5:1:2, 6:1:2, 7:1:2, 8:1:2, 9:1:2, 5:2:2, 6:2:2, 7:2:2, 8:2:2, 9:2:2, 5:3:2, 6:3:2, 7 The range is 3:2, 8:3:2, 9:3:2, 5:4:2, 6:4:2, 7:4:2, 8:4:2, 9:4:2, 5:5:2, 6:5:2, 7:5:2, 8:5:2, 9:5:2, 5:1:3, 6:1:3, 7:1:3, 8:1:3, 9:1:3, 5:2:3, 6:2:3, 7:2:3, 8:2:3, 9:2:3, 5:3:3, 6:3:3, 7:3:3, 8:3:3, 9:3:3, 5:4:3, 6:4:3, 7:4:3, 8:4:3, 9:4:3, 5:5:3, 6:5:3, 7:5:3, 8:5:3, 9:5:3, or falls within the range of any two of the above values.

[0122] In some embodiments, the conductive agent includes at least one of carbon, carbon black, graphite, expanded graphite, graphene, graphene nanosheets, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon fibers, carbon nanofibers, graphitized carbon sheets, carbon tubes, carbon nanotubes, activated carbon, and mesoporous carbon.

[0123] This solution does not impose any particular limitation on the negative electrode conductive agent, which can be any negative electrode conductive agent known in the prior art, as long as it can achieve the purpose of this application. For example, it can include, but is not limited to, at least one of the negative electrode conductive agents mentioned above.

[0124] In some embodiments, the adhesive includes at least one of polyacrylic acid, polymethacrylic acid, polyacrylate, polymethacrylate, polyacrylamide, styrene-butadiene rubber, acrylic styrene-butadiene rubber, acrylic acid-acrylonitrile-acrylamide copolymer, acrylic acid-acrylonitrile-acrylate copolymer, acrylonitrile-butadiene rubber, nitrile rubber, acrylonitrile-styrene-butadiene copolymer, acryloyl rubber, butyl rubber, fluororubber, polytetrafluoroethylene, polyvinyl alcohol, polyvinyl acetate, polyepoxychloropropane, polyphosphazene, polyacrylonitrile, polystyrene, latex, acrylic resin, phenolic resin, epoxy resin, carboxymethyl cellulose, sodium carboxymethyl cellulose, hydroxypropyl cellulose, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl cellulose, carboxymethyl chitosan, polyester, polyamide, polyether, polyimide, polycarboxylic acid ester, polycarboxylic acid, polyurethane, alginate, fluorinated polymer, chlorinated polymer, polyvinylidene fluoride, and poly(vinylidene fluoride)-hexafluoropropylene.

[0125] This solution does not impose any particular limitation on the adhesive, which can be any adhesive known in the prior art, as long as it can achieve the purpose of this application, such as including but not limited to at least one of the above adhesives.

[0126] In some embodiments, the negative electrode sheet further includes a negative current collector; the negative current collector includes a negative metal foil or a composite negative current collector.

[0127] In some implementations, the negative electrode metal foil includes copper foil.

[0128] In some embodiments, the composite negative electrode current collector includes a negative electrode metal foil and a negative electrode conductive layer disposed on at least one side of the negative electrode metal foil;

[0129] The conductive layer includes at least one of carbon, carbon black, graphite, expanded graphite, graphene, graphene nanosheets, carbon fiber, carbon nanofiber, graphitized carbon sheet, carbon tube, carbon nanotube, activated carbon, and mesoporous carbon.

[0130] This solution does not impose any particular limitation on the negative electrode metal foil; it can be any negative electrode metal foil known in the prior art, as long as it can achieve the purpose of this application. For example, it can include, but is not limited to, the aforementioned negative electrode metal foil. This solution also does not impose any particular limitation on the conductive layer of the composite negative electrode current collector; it can be any conductive layer known in the prior art, as long as it can achieve the purpose of this application. For example, it can include, but is not limited to, at least one of the aforementioned conductive layers.

[0131] This solution does not impose any particular restrictions on the negative electrode current collector, which can be any negative electrode current collector known in the prior art, as long as it can achieve the purpose of this application. For example, it can include, but is not limited to, at least one of the negative electrode current collectors mentioned above.

[0132] In some embodiments, the active material layer of the negative electrode sheet also includes a dopant;

[0133] The dopant includes at least one of Fe, Ni, Mn, Al, Mg, Zn, Ti, La, Ce, Sn, Zr, Ru, Si, and Ge.

[0134] This solution does not impose any particular restrictions on the dopant, which can be any dopant known in the prior art, as long as it can achieve the purpose of this application. For example, it can include, but is not limited to, at least one of the dopants mentioned above.

[0135] In some embodiments, the active material layer of the negative electrode sheet also includes additives.

[0136] In some implementations, the additives include thickeners;

[0137] Thickeners include at least one of cellulose thickeners, acrylate thickeners, and polyurethane thickeners; and / or,

[0138] Thickeners include at least one of sodium carboxymethyl cellulose, sodium hydroxymethyl cellulose, hydroxyethyl cellulose, polyacrylic acid, polyvinyl alcohol, and polyvinylpyrrolidone.

[0139] This solution does not impose any particular restrictions on the thickener, which can be any thickener known in the prior art, as long as it can achieve the purpose of this application. For example, it can include, but is not limited to, at least one of the thickeners mentioned above.

[0140] In some implementations, the additives include dispersants;

[0141] Dispersants include surfactant dispersants and / or polymeric dispersants.

[0142] In some embodiments, the dispersant includes at least one of polyvinylpyrrolidone, polyoxyethylene ether, hexadecyltrimethylammonium bromide, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, sodium lignosulfonate, polyacrylic acid, polymethacrylic acid, sodium polystyrene sulfonate, and sodium carboxymethyl cellulose.

[0143] This solution does not impose any particular limitation on the dispersant, which can be any dispersant known in the prior art, as long as it can achieve the purpose of this application. For example, it can include, but is not limited to, at least one of the dispersants mentioned above.

[0144] This solution does not impose any particular restrictions on additives, which can be any additives known in the prior art, as long as they can achieve the purpose of this application. For example, they can include, but are not limited to, at least one of the additives mentioned above.

[0145] This solution also provides an electrochemical device, which includes any of the negative electrode plates described herein.

[0146] The electrochemical devices provided in this solution include any device that performs an electrochemical reaction to convert chemical energy into electrical energy, including but not limited to all types of primary batteries, secondary batteries, fuel cells, solar cells, or capacitors.

[0147] In some embodiments, the electrochemical device includes a lithium secondary battery;

[0148] Lithium secondary batteries include lithium metal secondary batteries, lithium-ion secondary batteries, lithium polymer secondary batteries, or lithium-ion polymer secondary batteries.

[0149] In some embodiments, the electrochemical device includes an electrolyte, a positive electrode, and a negative electrode.

[0150] In some embodiments, the electrolyte includes at least one of a gel electrolyte, a solid electrolyte, and a liquid electrolyte.

[0151] In some embodiments, the liquid electrolyte includes a non-aqueous solvent;

[0152] Non-aqueous solvents include at least one of carbonate compounds, carboxylic acid ester compounds, and ether compounds.

[0153] In some embodiments, the carbonate compound may include at least one of diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl ethyl carbonate, ethylene carbonate, propylene carbonate, butyl carbonate, vinyl ethylene carbonate, fluoroethylene carbonate, 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, and trifluoromethylethylene carbonate.

[0154] This scheme does not have any particular restrictions on carbonate compounds, as long as they can achieve the purpose of this scheme, such as including but not limited to at least one of the carbonate compounds mentioned above.

[0155] In some embodiments, the carboxylic acid ester compound may include at least one of methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, decanoic acid lactone, valerate lactone, mevalonate lactone, caprolactone, and methyl formate.

[0156] This scheme does not have any particular restrictions on carboxylic acid ester compounds, as long as they can achieve the purpose of this scheme, such as including but not limited to at least one of the above-mentioned carboxylic acid ester compounds.

[0157] In some embodiments, the ether compound may include at least one of dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane, 2-methyltetrahydrofuran, and tetrahydrofuran.

[0158] This scheme does not have any particular restrictions on ether compounds, as long as they can achieve the purpose of this scheme, such as including but not limited to at least one of the above-mentioned ether compounds.

[0159] In some embodiments, the non-aqueous solvent includes at least one of dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolium ketone, N-methyl-2-pyrrolidone, formamide, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, and phosphate esters.

[0160] This method does not impose any particular restrictions on non-aqueous solvents, as long as they can achieve the purpose of this method. For example, it may include, but is not limited to, at least one of the non-aqueous solvents mentioned above. The use of non-aqueous solvents is unrestricted, as long as they can serve as a medium to facilitate the movement of ions participating in the electrochemical reaction of the battery.

[0161] In some embodiments, the liquid electrolyte includes lithium salts;

[0162] Lithium salts may include at least one of LiPF6, LiBF4, LiBOB, LiB(C6H5)4, LiB(C2O4)2, LiAsF6, LiCl, LiClO4, LiCH3SO3, LiCF3SO3, LiC4F9SO3, LiC(SO2CF3)3, LiN(SO2CF3)2, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiSiF6, LiSbF6, LiAlO4, LiAlCl4, LiI, and lithium difluoroborate.

[0163] This scheme does not impose any particular restrictions on lithium salts, as long as they can achieve the purpose of this scheme. For example, it may include, but is not limited to, at least one of the lithium salts mentioned above. The use of lithium salts is unrestricted, as long as they can participate in the ion movement of the battery electrochemical reaction.

[0164] In some embodiments, the lithium salt includes LiPF6. In the battery anode, indium enriched on the mesoporous surface of the coating material acts as an ion sieve layer, preferentially adsorbing PF6. - Anions promote Li +Rapid transport within the pores improves ion transport efficiency, thereby enhancing the rate performance of the battery.

[0165] This solution does not impose any particular restrictions on the electrolyte; it can be any electrolyte known in the prior art, as long as it can achieve the purpose of this application. For example, it can include, but is not limited to, at least one of the electrolytes mentioned above.

[0166] In some implementations, the electrochemical device includes a positive electrode.

[0167] In some embodiments, the positive electrode includes a positive current collector and a layer of positive active material disposed on at least one side of the positive current collector.

[0168] In some embodiments, the positive current collector includes a positive metal foil or a composite positive current collector;

[0169] Positive electrode metal foil includes aluminum foil; and / or,

[0170] The composite positive current collector includes a metal foil and a conductive layer disposed on at least one side of the metal foil.

[0171] This solution does not impose any particular restrictions on the positive electrode metal foil, which can be any positive electrode metal foil known in the prior art, as long as it can achieve the purpose of this application. For example, it can include, but is not limited to, at least one of the above-mentioned positive electrode metal foils.

[0172] This solution does not impose any particular limitation on the conductive layer, which can be any conductive layer known in the prior art, as long as it can achieve the purpose of this application. For example, it can include, but is not limited to, at least one of the conductive layers mentioned above.

[0173] This solution does not impose any particular restrictions on the composite positive current collector, which can be any composite positive current collector known in the prior art, as long as it can achieve the purpose of this application. For example, it can include, but is not limited to, at least one of the above-mentioned composite positive current collectors.

[0174] This solution does not impose any particular restrictions on the positive electrode current collector, which can be any positive electrode current collector known in the prior art, as long as it can achieve the purpose of this application. For example, it can include, but is not limited to, at least one of the positive electrode current collectors mentioned above.

[0175] In some embodiments, the positive electrode active material layer includes a positive electrode active material;

[0176] The positive electrode active material includes at least one of lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide.

[0177] This solution does not impose any particular restrictions on the positive electrode active material. It can be any positive electrode active material known in the prior art, as long as it can achieve the purpose of this application. For example, it can include, but is not limited to, at least one of the above-mentioned positive electrode active materials.

[0178] In some embodiments, the positive electrode active material includes a dopant. This solution does not impose any particular limitation on the dopant; it can be any dopant known in the prior art, as long as it achieves the purpose of this application. For example, it may include, but is not limited to, at least one of the dopants described above.

[0179] In some embodiments, the positive electrode active material layer includes a positive electrode binder;

[0180] The positive electrode binder includes at least one of polyvinylidene fluoride, poly(vinylidene fluoride)-hexafluoropropylene, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorinated acrylate resin, polyacrylic acid, polyacrylonitrile, polyimide, polyurethane, polyvinyl butyral, polyvinylpyrrolidone, acrylic acid-acrylonitrile-acrylamide copolymer, and acrylic acid-acrylonitrile-acrylate copolymer.

[0181] This solution does not impose any particular restrictions on the positive electrode binder, which can be any positive electrode binder known in the prior art, as long as it can achieve the purpose of this application. For example, it can include, but is not limited to, at least one of the positive electrode binders mentioned above.

[0182] In some embodiments, the positive electrode active material layer includes a conductive agent. This solution does not impose any particular limitation on the positive electrode conductive agent; it can be any positive electrode conductive agent known in the prior art, as long as it achieves the purpose of this application. For example, it can include, but is not limited to, at least one of the positive electrode conductive agents described above.

[0183] In some embodiments, the positive electrode active material layer includes additives.

[0184] This solution does not impose any particular restrictions on the positive electrode active material layer. It can be any positive electrode active material layer known in the prior art, as long as it can achieve the purpose of this application. For example, it can include, but is not limited to, at least one of the above-mentioned positive electrode active material layers.

[0185] This solution does not impose any particular restrictions on the positive electrode, which can be any positive electrode known in the prior art, as long as it can achieve the purpose of this application, such as including but not limited to the positive electrode mentioned above.

[0186] This solution also provides an electronic device, which is not particularly limited to the electronic device of this solution and can be any electronic device known in the prior art. The use of the electrochemical device of this solution is not particularly limited and can be used in any electronic device known in the prior art. According to some embodiments of this solution, the electronic device includes, but is not limited to, mobile phones, smartphones, laptops, tablets, wearable devices, smartwatches, smart bracelets, smart glasses, power banks, televisions, game consoles, game controllers, digital cameras, smart speakers, headphones, keyboards, mice, monitors, drones, audio equipment, home appliances, toys, power tools, automobiles, motorcycles, electric bicycles, bicycles, robots, robot dogs, industrial robots, android robots, etc.

[0187] Unless otherwise specified, the experimental methods used in the examples are conventional methods; the reagents used, unless otherwise specified, are commercially available reagents and materials. The source information of the raw materials used in the following examples and comparative examples is for illustrative purposes only and does not constitute any restriction on the procurement of raw materials. Those skilled in the art will know that the relevant raw materials can be obtained through other commercial channels or prepared by conventional methods in the art.

[0188] The CAS numbers and specifications of the main raw materials used in this application are shown in Table 1:

[0189] Table 1. Main Reagents in Examples and Comparative Examples

[0190]

[0191] Example 1

[0192] 1. Preparation of silicon-carbon anode materials:

[0193] 2.5 g of cetyltrimethylammonium bromide was dissolved in 250 mL of deionized water to obtain a cationic surfactant solution. Subsequently, 1 g of micron-sized silicon powder with a volumetric particle size distribution (Dv50) of 15 nm and a particle size distribution (SPAN) of 0.6 was added to the cationic surfactant solution. After magnetic stirring and ultrasonic treatment for 30 min, the mixture was vacuum filtered and then dried at 60 °C for 12 h to obtain silicon particles.

[0194] 5g of polyvinylpyrrolidone, 0.3g of silicon particles, 0.06g of indium trioxide and 0.1g of elemental sulfur were dispersed in 7mL of deionized water and stirred continuously at 55℃ for 12h. Then, the mixture was dried in a vacuum oven at 80℃ for 12h to obtain the precursor complex.

[0195] The precursor composite was placed in a tube furnace and subjected to high-temperature treatment under nitrogen protection, with a heating rate of 5℃ / min, a target temperature of 650℃, and a holding time of 2h. Then, it was subjected to planetary ball milling for 5h at a ball-to-material mass ratio of 1:35 and a rotation speed of 350r / min to obtain silicon-carbon anode material.

[0196] 2. Preparation of the negative electrode sheet:

[0197] A silicon-carbon anode material, conductive agent carbon black, and binder sodium carboxymethyl cellulose were mixed evenly in a mass ratio of 7:2:1. Then, an appropriate amount of deionized water was added, and the mixture was stirred continuously for 24 hours to obtain an anode slurry. Using a doctor blade coater and setting the wet film thickness to 100 μm, the slurry was evenly coated onto the surface of a copper foil current collector. Subsequently, it was dried in a vacuum oven at 80°C for 24 hours to obtain the anode sheet.

[0198] 3. The positive electrode is a commercially available lithium sheet.

[0199] 4. Electrolyte: It is prepared by mixing organic solvent and LiPF6 in a mass ratio of 92:8; wherein the organic solvent is a mixture of ethylene carbonate, diethyl carbonate, propylene carbonate, propyl propionate and ethylene carbonate in a mass ratio of 20:30:20:28:2.

[0200] 5. The separator is a commercially available porous polyethylene polymer film.

[0201] 6. Preparation of lithium-ion secondary batteries:

[0202] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes for safety isolation. The electrode assembly is then wound up to form the electrode assembly. The electrode assembly is placed in a packaging shell, electrolyte is injected, and the package is sealed to obtain a lithium-ion secondary battery.

[0203] Example 2

[0204] The difference between Example 2 and Example 1 is:

[0205] In silicon-carbon anode materials, the coating material has an average pore size of 10 nm and a specific surface area of ​​93 m². 2 / g;

[0206] The rest are as described in Example 1.

[0207] Example 3

[0208] The difference between Example 3 and Example 1 is:

[0209] In silicon-carbon anode materials, the coating material has an average pore size of 20 nm and a specific surface area of ​​137 m². 2 / g;

[0210] The rest are as described in Example 1.

[0211] Example 4

[0212] The difference between Example 4 and Example 1 is:

[0213] In silicon-carbon anode materials, the porosity of the coating material is 35% and the specific surface area is 114 m². 2 / g;

[0214] The rest are as described in Example 1.

[0215] Example 5

[0216] The difference between Example 5 and Example 1 is:

[0217] In silicon-carbon anode materials, the porosity of the coating material is 45% and the specific surface area is 136 m². 2 / g;

[0218] The rest are as described in Example 1.

[0219] Example 6

[0220] The difference between Example 6 and Example 1 is:

[0221] In silicon-carbon anode materials, the specific surface area of ​​the coating material is 90 m². 2 / g;

[0222] The rest are as described in Example 1.

[0223] Example 7

[0224] The difference between Example 7 and Example 1 is:

[0225] In silicon-carbon anode materials, the specific surface area of ​​the coating material is 140 m². 2 / g;

[0226] The rest are as described in Example 1.

[0227] Example 8

[0228] The difference between Example 8 and Example 1 is:

[0229] In silicon-carbon anode materials, based on the mass of porous carbon material, the mass ratio of indium particles is a, and a is 6.67%.

[0230] The rest are as described in Example 1.

[0231] Example 9

[0232] The difference between Example 9 and Example 1 is:

[0233] In silicon-carbon anode materials, based on the mass of porous carbon material, the mass ratio of indium particles is a, where a is 10%.

[0234] The rest are as described in Example 1.

[0235] Example 10

[0236] The difference between Example 10 and Example 1 is:

[0237] In silicon-carbon anode materials, the average volumetric particle size of indium particles is 3 nm;

[0238] The rest are as described in Example 1.

[0239] Example 11

[0240] The difference between Example 11 and Example 1 is:

[0241] In silicon-carbon anode materials, the average volumetric particle size of indium particles is 5 nm;

[0242] The rest are as described in Example 1.

[0243] Example 12

[0244] The difference between Example 12 and Example 1 is:

[0245] In silicon-carbon anode materials, the volumetric particle size Dv50 of silicon particles is 10 nm.

[0246] The rest are as described in Example 1.

[0247] Example 13

[0248] The difference between Example 13 and Example 1 is:

[0249] In silicon-carbon anode materials, the volumetric particle size Dv50 of silicon particles is 13 nm;

[0250] The rest are as described in Example 1.

[0251] Example 14

[0252] The difference between Example 14 and Example 1 is:

[0253] In silicon-carbon anode materials, the particle size distribution SPAN value (Dv90-Dv10) / Dv50 of silicon particles is 1.2;

[0254] The rest are as described in Example 1.

[0255] Example 15

[0256] The difference between Example 15 and Example 1 is:

[0257] In silicon-carbon anode materials, the particle size distribution SPAN value (Dv90-Dv10) / Dv50 of silicon particles is 0.3;

[0258] The rest are as described in Example 1.

[0259] Example 16

[0260] The difference between Example 16 and Example 1 is:

[0261] Based on the mass of the silicon-carbon anode material, the mass ratio of silicon particles is b, and b is 35%;

[0262] The rest are as described in Example 1.

[0263] Example 17

[0264] The difference between Example 17 and Example 1 is:

[0265] Based on the mass of the silicon-carbon anode material, the mass ratio of silicon particles is b, where b is 45%.

[0266] The rest are as described in Example 1.

[0267] Comparative Example 1

[0268] The difference between Comparative Example 1 and Example 1 is as follows:

[0269] No indium trioxide added;

[0270] The rest are as described in Example 1.

[0271] Comparative Example 2

[0272] The difference between Comparative Example 2 and Example 1 is as follows:

[0273] In silicon-carbon anode materials, the coating material has an average pore size of 7 nm and a specific surface area of ​​65 m². 2 / g;

[0274] The rest are as described in Example 1.

[0275] Comparative Example 3

[0276] The difference between Comparative Example 3 and Example 1 is as follows:

[0277] In silicon-carbon anode materials, the coating material has an average pore size of 25 nm and a specific surface area of ​​148 m². 2 / g;

[0278] The rest are as described in Example 1.

[0279] Comparative Example 4

[0280] The difference between Comparative Example 4 and Example 1 is as follows:

[0281] In silicon-carbon anode materials, the porosity of the coating material is 30% and the specific surface area is 10¹ m². 2 / g;

[0282] The rest are as described in Example 1.

[0283] Comparative Example 5

[0284] The difference between Comparative Example 5 and Example 1 is as follows:

[0285] In silicon-carbon anode materials, the porosity of the coating material is 50% and the specific surface area is 167 m². 2 / g;

[0286] The rest are as described in Example 1.

[0287] Test method:

[0288] 1. Specific surface area and pore size: 50 mg of dried silicon-carbon anode material was placed in a sample tube and degassed under vacuum at 150 °C for 6 hours. Then, nitrogen adsorption experiments were performed using a Micromeritics ASAP 2460 analyzer at a liquid nitrogen temperature of 77 K. The phase set relative pressure P / P0 ranged from 0.01 to 0.99. The specific surface area and pore size of the silicon-carbon anode material coating were tested.

[0289] 2. Porosity: The apparent volume of the silicon-carbon anode material and the volume of the silicon particles are measured and denoted as V and Va, respectively. 硅 The true volume of the silicon-carbon anode material was then measured sequentially using an HX-TD type true density meter and recorded as V. 真 Porosity (%) = (1-V) 真 -V 硅 )*100 / V, calculate the porosity of the silicon-carbon anode material coating.

[0290] 3. Particle size: The particle size of indium particles and silicon particles in silicon-carbon anode material were measured using a Topsizer laser particle size analyzer, and the SPAN value of silicon particle size distribution was calculated.

[0291] 4. Electrochemical impedance: After the silicon-carbon anode material is fabricated into a battery, the electrochemical impedance of the silicon-carbon anode material is obtained by using a Bio-Logic VMP3 electrochemical workstation with a frequency scan range of 100kHz to 10mHz and an excitation signal amplitude of 5mV.

[0292] 5. Battery expansion rate: After the silicon-carbon anode material is made into a battery, it is charged 50 times at a rate of 0.1C in an environment of 25℃ and 0.8MPa. The thickness change of the battery is recorded by a laser displacement sensor with an accuracy of -0.1μm to 0.1μm, and recorded as H before and H after respectively. The expansion rate is calculated by the formula: Expansion rate = (H after - H before) / H before * 100%.

[0293] 6. Rate test: After the silicon-carbon anode material is made into a battery, it is charged and discharged 5 times at 0.2C, 1C and 2C rates in an environment of 25℃. The discharge capacity of the 5th cycle is recorded as the test result at that rate.

[0294] 7. Initial Coulombic Efficiency: After the silicon-carbon anode material is fabricated into a battery, the battery is connected to an ASD936 charge-discharge tester, ensuring that the positive and negative terminals are not reversed. Then, it is charged at a 0.1C rate, and the voltage, current and time are monitored until the upper limit voltage of 4.3V is reached. Then, it is discharged at a constant current rate of 0.1C until the final voltage is 3V. At the same time, the change of the battery's discharge rate with the discharge time is recorded. Based on the discharge rate, the initial coulombic efficiency of the battery is calculated.

[0295] 8. Cycle Capacity Retention: After fabricating the silicon-carbon anode material into a battery, it was charged at 0.1C rate in an environment of 25℃ until the upper limit voltage reached 4.3V, and then discharged at a constant current rate of 1C until the final voltage reached 3V. The discharge capacity of the first cycle was recorded as C1. After repeating the charge-discharge cycle 200 times, the discharge capacity of the 200th cycle was recorded as C1. 200 Repeat the test on C1 and C of five batteries respectively. 200 And calculate C respectively 200 *100% / C1, take the average value as the battery's cycle capacity retention rate.

[0296] Some process parameters of Examples 1 to 17 and Comparative Examples 1 to 5 are shown in Table 2.

[0297] Table 2. Partial process parameters of Examples 1-17 and Comparative Examples 1-5

[0298]

[0299]

[0300] According to the above test methods, the performance of the separators prepared in Examples 1 to 17 and Comparative Examples 1 to 5 were tested respectively; the performance data of Examples 1 to 17 and Comparative Examples 1 to 5 are shown in Table 3.

[0301] Table 3. Performance data of Examples 1-17 and Comparative Examples 1-5

[0302]

[0303]

[0304] As can be seen from Tables 2 and 3:

[0305] Combining Examples 1 to 7 and Comparative Examples 2 to 5, the electrochemical impedance of the comparative examples increased by at least 33 Ω, verifying that controlling the pore size and porosity of the coating material, and adjusting its specific surface area, helps improve electron and ion transport efficiency in synergy with indium particles. Furthermore, the battery expansion rates of Examples 1 to 7 were 39%–45%, while those of Comparative Examples 2 to 5 were 68%–87%, and the discharge capacity at different rates decreased by at least 308 mAh / g compared to Examples 1 to 7, with initial coulombic efficiency and capacity retention decreasing by at least 8.2% and 26%, respectively. This verifies that a coating material with suitable pore size and porosity, combined with its specific surface area, helps buffer the volume expansion of the silicon-carbon anode material, reducing the battery expansion rate, thereby improving the battery's rate capability, cycle life, and initial coulombic efficiency.

[0306] Referring to Examples 1 and 8 to 11, the electrochemical impedance was between 28Ω and 40Ω, the battery expansion rate was between 40% and 59%, the discharge capacity at different rates fluctuated between 153 and 265 mAh / g, and the capacity retention rate was between 73.8% and 81.2%. This indicates that by controlling the mass ratio and average particle size of indium particles within a certain range, and in conjunction with the porous structure of the coating material, electron and ion transport can be promoted. Furthermore, indium can synergistically suppress silicon expansion with porous carbon materials, effectively improving the battery's volume expansion, rate capability, and cycle performance.

[0307] Referring to Examples 1 and 12 to 15, the electrochemical impedance was between 27Ω and 36Ω, the battery expansion rate was between 38% and 49%, the maximum difference in discharge capacity at different rates was only 157mAh / g, and the capacity retention rate was between 76.6% and 81.2%. This confirms that controlling the particle size and particle size distribution of silicon particles, in synergy with indium and porous carbon materials in the coating material, can regulate the volume expansion of silicon-carbon anode materials, improve electron transport and ion diffusion efficiency, effectively reduce battery expansion rate, and help maintain battery rate and cycle capacity.

[0308] Further combining Examples 16 and 17, based on the quality of the silicon-carbon anode material, the mass ratio of silicon particles increased from 35% to 45%, the electrochemical impedance increased from 32Ω to 37Ω, the maximum difference in discharge capacity at different rates was only 239mAh / g, and the battery expansion rate changed from 45% to 53%. This shows that increasing the silicon content of the silicon-carbon anode material, while slightly sacrificing the battery expansion rate, not only promotes electron transport but also improves the rate performance of the battery.

[0309] Compared with Comparative Example 1, the battery expansion rate increased to 102%, the electrochemical impedance increased to 689Ω, and the discharge capacity at 0.2C, 1C, and 2C rates decreased to 1357mAh / g, 1012mAh / g, and 727mAh / g, respectively. The initial coulombic efficiency decreased to 79.3%, and the capacity retention rate decreased to 40.1%. Furthermore, Comparative Example 1 showed structural pulverization, which confirms that the silicon-carbon anode material provided in this solution, with its porous structure in the coating material working synergistically with porous carbon materials and indium, effectively improves the battery's volume expansion and enhances its rate and cycle performance.

[0310] The above description is only a part or preferred embodiment of this application. Those skilled in the art should understand that the above embodiments should not be construed as limiting the scope of protection of this application. All equivalent structural transformations made using the content of this application specification under the overall concept of this application, or direct / indirect applications in other related technical fields, are included within the scope of protection of this application.

Claims

1. A silicon-carbon negative electrode material, characterized in that, The silicon-carbon negative electrode material comprises a core material and a coating material, the core material comprises silicon particles, the coating material comprises porous carbon material doped with indium particles, the average pore size of the coating material is 10-20 nm, and the porosity of the coating material is 35-45%.

2. The silicon-carbon negative electrode material of claim 1, wherein, The specific surface area of the coating material is 90 m 2 / g to 140 m 2 / g.

3. The silicon-carbon negative electrode material of claim 1, wherein, The average volume particle size of the indium particles is 1-5 nm.

4. The silicon-carbon negative electrode material of claim 3, wherein, The mass ratio of the indium particles to the porous carbon material is a, and 6.67%≤a≤10% based on the mass of the porous carbon material.

5. The silicon-carbon negative electrode material of claim 1, wherein, The volume particle size Dv50 of the silicon particles is 10-15 nm.

6. The silicon-carbon negative electrode material of claim 5, wherein, The particle size distribution SPAN value (Dv90-Dv10) / Dv50 of the silicon particles is ≤1.

2.

7. The silicon-carbon negative electrode material of claim 6, wherein, The mass ratio of the silicon particles to the silicon-carbon negative electrode material is b, and 35%≤b≤45% based on the mass of the silicon-carbon negative electrode material.

8. A negative electrode sheet characterized by comprising: The negative electrode sheet comprises the silicon-carbon negative electrode material according to any one of claims 1-7.

9. The negative electrode sheet according to claim 8, characterized by, The negative electrode sheet further comprises a conductive agent and a binder, and the mass ratio of the silicon-carbon negative electrode material, the conductive agent and the binder is (5-9):(1-5):(1-3).

10. An electrochemical device, characterized by, The electrochemical device comprises the negative electrode sheet according to claim 8 or 9.

11. An electronic device, comprising: The electronic device comprises the electrochemical device according to claim 10.

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